Azat Khuzhin 18e8f0eb5e Add ability to push down LIMIT for distributed queries ... This way the remote nodes will not need to send all the rows, so this will decrease network io and also this will make queries w/ optimize_aggregation_in_order=1/LIMIT X and w/o ORDER BY faster since it initiator will not need to read all the rows, only first X (but note that for this you need to your data to be sharded correctly or you may get inaccurate results). Note, that having lots of processing stages will increase the complexity of interpreter (it is already not that clean and simple right now). Although using separate QueryProcessingStage looks pretty natural. Another option is to make WithMergeableStateAfterAggregation always, but in this case you will not be able to disable only this optimization, i.e. if there will be some issue with it. v2: fix OFFSET v3: convert 01814_distributed_push_down_limit test to .sh and add retries v4: add test with OFFSET v5: add new query stage into the bash completion v6/tests: use LIMIT O,L syntax over LIMIT L OFFSET O since it is broken in ANTLR parser https://clickhouse-test-reports.s3.yandex.net/23027/a18a06399b7aeacba7c50b5d1e981ada5df19745/functional_stateless_tests_(antlr_debug).html#fail1 v7/tests: set use_hedged_requests to 0, to avoid excessive log entries on retries https://clickhouse-test-reports.s3.yandex.net/23027/a18a06399b7aeacba7c50b5d1e981ada5df19745/functional_stateless_tests_flaky_check_(address).html#fail1		2021-06-09 02:29:50 +03:00
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completions	Add ability to push down LIMIT for distributed queries	2021-06-09 02:29:50 +03:00
CMakeLists.txt